Several different types of document feeder devices are in common use in the prior art. These include belt or web type feeders, roll type feeders, and mechanical punch type feeders. Web type feeders exist which are designed to receive documents, such as individual envelopes which are standing vertically in a horizontally extending stack, and feeding the envelopes one at a time in a path perpendicular to the horizontal extent of the stack. In more efficient devices, the web which contacts the envelopes is normally perforated, and a vacuum force is applied to the face of the web which is in contact with the envelope. The vacuum force extends through the perforations in the web, and holds the first envelope in the stack in contact with the web as the web transports the envelope towards a work station.
Most sheet material processing devices such as envelope transporters can only be efficiently and economically designed to handle envelopes of different sizes which are processed at different times through the apparatus. However, present web feed devices include a movable web surface that is of a single length, and that length is necessarily fixed to handle the largest size envelope contemplated for use in the particular apparatus. In many such envelope feed devices, however, it has been found that the trailing corners of smaller envelopes become caught in the perforations of the web, which results in tearing or crumbling of the envelope, or causing more than one envelope from the stack to be engaged and transported by the web. When the feed web is initially designed to handle large sized business envelopes, but the apparatus is ultimately called upon to handle smaller envelopes, such as remittance envelopes, the smaller envelopes tend to get caught in the perforations, resulting in a malfunction of the feeder device, and ultimately causing jamming or other malfunctions of the apparatus in which the envelope is being fed for processing.
This defect in currently available web type envelope feeders has reduced the efficiency, workability, and commercial acceptance of prior art web type envelope feed devices. An object of the present invention, therefore, is to provide a novel web type envelope or sheet material feed device which comprises a feed web where the effective contact surface can be selectively varied to accommodate envelopes of different sizes without causing the corners of the envelopes to be caught in the perforations in the web.
A further object of the present invention is to provide a perforated web type sheet material feed device having a suction force applied through perforations in the web to engage and advance the sheet material to a work station as the web moves, wherein the effective contact surface of the web can be selectively varied to prevent the corners of the sheets from being caught by the perforations in the web.
Still another object of the present invention is to provide a web-type sheet material feed device wherein the pressure of the accumulated stack of sheet material bearing against the web is automatically controlled to permit the sheet material to be fed one at a time.
These and other objects and features accomplished by the present invention will be better understood with reference to the following summary of the invention, drawings, and detailed description thereof.